Patent documents No. 1 and No. 2 disclose water turbine power generators each comprising a power generation mechanism and a locking mechanism for engaging the power generation mechanism with a support member, wherein the power generation mechanism comprises a water turbine unit and a power generator unit, wherein the water turbine unit comprises a vertically extending cylindrical casing provided with a water inlet port at an upper part of a circumferential side wall and a water outlet port at a lower end, and an impeller installed in the cylindrical casing, and wherein the locking mechanism locks the cylindrical casing of the water turbine unit on a damming board which is installed in a canal to form a support member.